The present invention relates generally to insulation for exhaust systems and other types of pipe systems that transport hot gases and other hot fluid materials. More specifically, the present invention relates to a multi-component sleeve that may be used, among other things, to fit exhaust systems on vehicles generally and large trucks in particular.
Heretofore, various insulation systems have been used to insulate automotive and industrial exhaust systems. Exhaust insulation systems are used to maintain high temperature of exhaust gases in order to provide more efficient and complete combustion of fuels, and to protect surrounding components from the high exhaust temperatures. Additionally, maintaining high exhaust temperatures tends to increase the velocity of the exhaust gases through the system, which allows the engine cylinder to more fully evacuate and aids in the emission control processes. On large bore diesel trucks, insulating the exhaust system has been shown to improve the performance of the emission control system located in the exhaust stream system.
U.S. Pat. No. 6,610,928 discloses a sleeve for providing thermal insulation to elongated substrates, formed from a composite sheet having a tough, resilient reinforcing layer to which a metallic reflective layer is attached on one side and a fibrous, non-woven insulative layer is attached on the opposed side. The sleeve includes a seam, formed lengthwise along the sleeve in spaced relation to the reverse fold, defining a central space for receiving elongated substrates.
U.S. Pat. No. 6,978,643 is directed to a multilayer sleeve for insulating or protecting elongated substrates, wherein the sleeve is continuously knitted in different sections integrally joined end to end, the sections being formed of different filamentary members chosen for desired characteristics. The sleeves are formed into the multilayer configuration by reverse folding the sleeves inwardly to place one section coaxially within another.
U.S. Pat. No. 5,134,846 discloses a cover for insulating exhaust systems of internal combustion engines comprising a tubular shaped layer of insulating material circumscribingly engaging the exhaust system and a flexible metal sleeve for protecting the insulating material and holding the insulating material against the exhaust system. The cover is held in place by hose clamps or tie wraps.
U.S. Pat. No. 5,092,122 is directed to a means and method for insulating automotive exhaust pipes by sliding a flexible insulated tube over the exhaust pipe. The tube comprises concentrically arranged inner and outer corrugated stainless steel tubes, with the annulus between the corrugated tubes filled with refractory fiber insulation.
U.S. Pat. No. 5,617,900 includes a thermally insulative sleeve with a seamless, hollow flexibly resilient inner tubular member woven of strand material including at least one metal wire strand, a separate, integral, at least essentially unbroken, metal surface member applied over the inner tubular member extending along and at least essentially completely surrounding the inner tubular member and a flexible outer cover also woven of strand material extending along and completely around the inner tubular member and metal surfaced member securing the metal surface member with the inner tubular member and offering some degree of protection. The inner tubular member may be knit from wire or from a combination of wire and glass fiber yarn, the latter providing some thermal insulative protection.
U.S. Patent Application Publication No. 2002/0168488 discloses a protective sleeve for covering elongated substrates, wherein the sleeve is knitted from a combination of first and second filamentary fibers having different properties from one another. The filamentary members are plated so that the filamentary members with properties compatible with the substrate are positioned predominantly on the inner surface of the sleeve facing and engaging the substrate. Filament properties include heat resistance, high tensile strength, resistance to abrasion, chemical attack and damping capability. The sleeve includes ribs integrally knitted lengthwise along the sleeve to form insulating air pockets, and the ends of the sleeve are finished with welts to prevent unraveling.
Unfortunately, many of these prior art exhaust insulation sleeves suffer from various drawbacks. Some are expensive to manufacture and difficult to install on exhaust systems. Some require specialized tooling for each distinct pipe geometry. Many do not provide sufficient breathability, so that when the insulation is exposed to water and rain, the water soaks into the insulation and does not dry quickly, which leads to rust and corrosion within the exhaust system. Because these type systems are subject to large temperature fluctuations, sometimes more than a 1000° F., from start-up to upper operating temperatures and fluctuations within operating temperatures, there is a need for insulating systems to breathe to some degree. Further, particularly in colder climates and coastal climates, salt from the roads can infiltrate the insulation system and accelerate corrosion of the system. Moreover, many of the insulation sleeves and systems are made from materials that do not maintain their structural integrity over time due to wear and tear, and further degrade from the exposure to high temperatures associated with exhaust systems. Therefore, it would be desirable to provide a breathable, tough, resilient insulating system that can withstand the rigors of exposure to high temperatures, salt, water, and general wear and tear, which is inexpensive and easy to manufacture and install.